In many fields of endeavor it is important to be able to determine whether or not substances are contaminated with biologically active agents such as bacteria and the like. Examples of such fields are the medical field, the food processing industry, the pharmaceutical industry, the cosmetics industry, the field of public health, and the preparation of interplanetary space vehicles.
In the past, it has been a standard practice to place a sample of a material to be tested for the presence of biologically active agents in an appropriate growth medium on a Petri dish and to make visual observations of the resulting microbial growth, if any. Not only are such culturing methods slow and laborious, but because they depend on the subjective judgment of individual human observers, the result obtained is not uniformly reliable.
Techniques have also been developed for detection of bacteria which involve incubation of a sample of material to be tested in a closed container with a radioactive isotope labeled culture medium and monitoring the atmosphere in the container above the medium to determine whether or not radioactive gases are produced. A system of this type is disclosed in U.S. Pat. Nos. 3,676,679 and 3,935,073. Such systems are rapid and reliable, but they suffer from a number of disadvantages. In the first place, radioactively labeled materials are not inexpensive and require special handling during storage, use and disposal. Moreover, although the levels of radioactivity encountered in using such systems are very low, prospective users may be deterred by personal fears of radioactivity. The use of radioactive isotopes in instrumental systems has generally been considered necessary in order to facilitate detection of minute quantities of metabolic product gases thereby to detect the presence of biologically active species. There exists a need for an instrumental system for measuring metabolically produced non-radioactive gases to detect bacteria and the like.
Accordingly, it is an object of the present invention to provide a rapid method for detecting the presence or absence of biologically active agents.
Another object of the invention is to provide a method for detecting the presence or absence of biologically active agents which uses comparatively inexpensive materials.
It is a further object of the present invention to provide an instrumental method for detecting the presence or absence of biologically active agents which is not subject to the vagaries of subjective human observations.
Another object of the present invention is to provide an instrumental system for detecting the presence or absence of biologically active agents which avoids the use of radioactive materials.
Further objects of the invention will be apparent from a consideration of the following description.